A recombinant viral vector carrying a foreign DNA insert may be used to deliver genes to cells, where the gene may be expressed to permit production of polypeptides or polynucleotides (e.g., miRNA, RNAi, antisense RNAs) for the treatment or amelioration of diseases or genetic defects in humans or non-human mammals. The foreign DNA insert may also be used for DNA recombination and repair of genes, and no expression would necessary under such circumstances.
Recombinant viral vectors that are commonly used in gene delivery applications are typically defective in one or more genes that are required for viral reproduction, so that the recombinant viral vectors cannot reproduce themselves in patients receiving the treatment. During the production of a recombinant virus, the defective gene or genes are provided in trans, i.e., from a DNA sequence that is physically separated from the recombinant viral genome, so as to permit replication and encapsidation of the recombinant virus. However, since the DNA sequence and the recombinant viral genome are both present in the nucleus of the host cell, recombination events between the DNA sequence and the recombinant viral genome may result in replication-competent viruses that are undesirable for treatment purpose.
Therefore, there still exists a need for methods that are capable of producing recombinant viral vectors that are not contaminated with replication competent viruses and that can be easily scaled-up for industrial production.